Investigation on Cutting Fluid Penetration Kinetics and Friction Reduction Mechanism of Micro-Textured Tools via...

Severe friction and extreme temperatures occur at the tool-chip interface during metal cutting. Conventional cutting fluids struggle to penetrate interface micro-capillaries at the contact interface under high contact pressure. This issue causes severe tool-chip adhesion and accelerates tool wear. This study aims to solve fluid delivery limitations by introducing micro-textures with a depth of 15 microns on the tool surfaces. It reveals the mechanism of micro-textures in accelerating fluid penetration and reducing interface friction. An analytical capillary penetration model was established for conventional and micro-textured tools. Thermal penetration tests (30-150 °C) and turning experiments on hardened steel were conducted to evaluate interfacial fluid transport behavior. Theoretical modeling shows that micro-textures facilitate direct vapor-phase filling into micro-capillaries. This mechanism bypasses liquid ingress and droplet evaporation stages. This reduces the fluid penetration time into the capillaries by almost an order of magnitude. Thermal tests show that textured surfaces maintain dynamic vapor-liquid equilibrium. At 150 °C, the vapor penetration area reaches 978.5 × 10^-3 mm² on micro-textures, over four times that of smooth surfaces. Energy dispersive spectrometry (EDS) detected fluid-derived sodium (0.98 at.%) inside micro-textured capillaries. Meanwhile, workpiece material adhesion decreases from 6.04 at.% to 0.11 at.%. In turning tests of AISI 1045 hardened carbon steel, micro-textured tools reduced the main cutting force by up to 17% and the axial force by up to 22%. Cutting temperatures decreased by up to 10.0%. The average tool-chip friction coefficient dropped by 9.2% at a cutting speed of 240 m/min. This work provides insights into a vapor-phase lubrication mechanism and offers quantitative guidance for designing high-efficiency self-lubricating tools.